Lighting system



Aug. 20, 1935. H. M. CAVANAUGH LIGHTING SYSTEM Filed June 27, 1933 animproved illuminating device using gaseous il,-'

, pass through the tubes.

' continuation in part of my application Ser. -No.

671,886 filed May 19, 1933.

'An object of the invention is to provide anim- Patented Aug. 2 1935[Qumran STATES Howard M. Cavanaugh, Bufl'alo, N. Y., assignor to DayliteTubes, Inc -Buffalo, N. Y., a corporation of New York Application June2'7, 1933, Serial No. 6 77, 8d3- Claims. (cine-124) 1 This inventionrelates to gaseous illuminating tubes, and particularly to lightingsystems and apparatus therefor. When such tubes are operated by acurrent of relatively low volta'ge, it is necessary to ionize the gastherein before current will This application is a proved lighting systemfor gaseous illuminating tubes, with which greater efliciency in theoperation ofsaid tubes may be obtained; with which the flow ofilluminating current through the i1 luminating tubes may be initiated ina simple manner; with which the apparatus required to initiate the flowoflighting current through such illuminating tubes may be reduced to aminimum;

and with which the starting of the illumination'ot j improved means forcausing ionization of the gas of low voltage gaseous illuminating tubesto initi-' ate the flow of current therethrough, which will be automaticin action, have a long life, and be dependable and relatively slmple'andinexpensive in construction.

Another object of the invention is to provide an improvedstarting tubewhichmay be advan tageously used as a-partof theystarting mechanism forlow voltage gaseous illuminating tubes. Another object of the inventionis; toprovide luminating tubesof the low voltage type,.with which onemay produce a white light which closely resembles daylight in-itscharacteristics and which will have maximum eillciency, unip v vsupplied from line wires L L The line wires Ll, L are connected to theprimary winding l3 formity and dependability.

' Various other objects and advantages ,will be apparent from the--following description or an embodiment of the invention, and the-noveltea-- tures will be particularly pointed out'hereinafter' in connectionwith thrrappended,claims; v

In' the accompanying drawing: I Fig. 1 is a plan of a lighting deviceconstructed in accordance with this invention. I

Fig. 2 is a diagram of a system by which the lighting of low voltagegaseous illuminating tubes may be initiated and maintained in accordancewith this invention. I

Fig. 3 is a side elevation of a starter tube which may be used to ionizethe gas in the illuminating tubes, and a choke coil, schematicallyshown, arranged in operative relation to the starter tube.

In the illustrated-embodiment of the invention, the lighting system isapplied to a pair of low voltage, gaseous illuminating tubes l0 and IIFig.

1, which are arrangedin a close or compact rela-.

' tion to one anotherso that the light rays emitted byboth tubes willlargely; or, entirely mix immediately after leaving the tubes. The tubescontain gases which impart color to the light rays that are emitted bysuch tubes when illuminated, andthe. gases selected for the tubes arethose which will cause the" tubes-f'to' emit different colored lightswhich are complementary to one another, such as blue and red.' Forexample, one tube may contain a gas, such as argon,'krypton, or xenon,each plus mercury, which 0 'es'it to mit a blue color Y hertube' maycontain causes it to emit a red "these tubes; can thetube, l0,-is.made

"i approximately of a narrow u-shape, and the other tube II is disposedbetweenv the arms of the U, so as-to provideas concentrated a source oflight as "possible. Any other arrangement by which the two tubes may beplaced in' close proximity to one' another. andcause a'mixing of thelight rays promptly after emission from the tubes may be utilized, andsuitablefreflecting means l2 may be disposedback of these tubes l0 and lI so as to direct as many as possible or the light rays'irom the tubesinto crossing paths whereby a maximum portion of the light from thedifferent tubes will mix; 1

In the illustrated example of the invention, the

1 tube, I0 is 'of the double anode type, and the tube H of the singleanode type, and the tubes are 1 connected electrically in series to oneanother. The lighting current for such tubes is alternating currentofany suitable frequency, which is of a suitable transformer, preferablyone of the leakage type, and magnetic shunts may be provi'ded fora pairof secondary windings l4 and the end opposite its connection to the wirel6, by

a wire I 9 to the other-anode 20 of the double anode tube It). Asuitable condenser 2| is connected between the wires l1 and I9 whichlead to the anodes l8 and 20 and serves as a power factor correction forthe tube Ill.

The cathode 22 of the tube I0 is thermionic and, by way of example, isshown as of the filament type which is heated by a low voltage currentobtained from a secondary winding 23 arranged in inductive relation tothe primary winding I3. The anode 24 of the single anode tube II isconnected by a wire 25 to the cathode 22.0f the tube Ill. The cathode 26of the tube II is also thermionic and is illustrated as of the filamenttype, similarly heated by a low voltage current obtained from asecondary winding 21 that is also arranged in inductive relation to theprimary winding l3. A wire 28 connects the cathode 26 of the tube H toone side of a choke coil 29, the other side of the choke coil beingconnected by a wire 38 to the wire l6 which connects inseries thesecondary transformer windings l4 and IS. The windings l4 and I5 may beconsidered as one seeondary, with the wire 39 connected to anintermediate point of that one secondary.

- The choke coil 29 may, for convenience, be constructed as showndiagrammatically in Fig. 3, so as to have a partially closed magneticcircuit with an air gap 3|, and this air gap is utilized as part of theapparatus for the ionizing of the gas in the illuminating tubes I0 and lI, and when illumination of those tubes is to be started. For thispurpose I provide a tube or envelope 32 which may, for convenience, bemade of glass, and in this envelope or tube is provided a-fixed contact33 suitably supported by a stem 34, to which is connected 'a conductor35 which extends through one end of the envelope to the exterior is,in-eflect, an armature carried by the spring 38-,

which serves as a resilient support therefor. The spring 38 yieldinglyand resiliently urges the contact 36, carried thereby, into engagementwith the fixed contact 33, and at this time the armature or plate 31 isspaced from the walls of the envelope so that the armature or plate 31and the contact 36 may move away from the fixed contact 33land break theengagement or connection between the contacts 33 and 36.

The envelope or tube 32 is disposed in proximity to the air gap 3| ofthe choke coil, or otherwise in a position to be influenced by themagnetic field set up by the choke coil at the air gap 3| thereof, whenthe choke coil is energized. The tube or envelope 32 is so disposed withrespect to the air gap or choke coil that when the choke coil isenergized the magnetic field set up thereby will attract the armature orplate 31 and magnetically pull it, against the stress of the spring-.38,away from the contact 33, and open the connection between the conductors35 and 40. When the choke coil 29 is de-energized, the magneticattraction on the plate 31 will stop, and the spring 38 will return thecontact 36 into engagement with the contact 33. g The conductor 40 ofthe starter tube is corinected to the wire l9 leading from the secondary15 to the anode 20 of the tube 10. and conductor 35 of the starter tubeis connected to the wire 28 which connects the cathode of the tube l lto the cloke coil 29. The envelope or tube 32 is preferably gas tightand exhausted to a high vacuum, such as one of approximately 0.1 micronsof mercury pressure, and all parts within the envelope or tube as wellas the walls of the tube are thoroughly degasified so as to remove allimpurities.

It will be noted that the tubes l0 and II are connected electrically inseries to one another and the operation is as follows:

When the current is applied to the primary Winding l3 of thetransformer, it induces alterhating currents in the secondary windingsl4, I5, 23 and 21. The currents induced in the windings 23 and 21 willimmediately flow through the cathode filaments 22 and 26 respectivelyand heat them to emission temperatures. Currents induced in thesecondary windings l4 and I5 will tend to flow through the wires H and[9 to the anodes l8 and 20 of the tube l9. From the wire l6, connectingthe windings l4 and IS, the circuit to the tube I0 is completed throughwire 30, choke coil 29 and wire 28 to the tube II, and through the tubeII and wire 25 to the cathode of the tube I'll. By this arrangement inwhich --the.A. C. current is applied to the tube In, a cur rent willflow in tube l0 between the anodes l8 and 20 and the cathode 22, onehalf of each complete current wave passing between the anode l8 andcathode 22, and the other half between the anode 20 and the cathode 22.

Alternating current so passing through the tube [0 will be rectified,and will flow through the wire 25 to anode 24 of the tube H, thencethrough the tube I I to the cathode 26 of that tube, and thence throughwire 28, choke coil 29 and wire 39 back to the transformer windings I4and [5. It will be noted that the rectified current which passes throughthe tube I8 is also the illuminating current for the tube II, and wehave a condition of having two low voltage, gaseous illuminating tubesconnected in series to one another, with one of such tubes, such as thetube ll, operated by the direct current which is rectified in the otheror double anode tube Hi.

When current is applied to the primary winding l3 to start theillumination of the tubes l0 and II, no current will flow through thetubes l0 and H until the gas in such tubes has first been ionized, andin the illustrated example of the invention, this ionization isaccomplished through thestarter tube 32. Current will, however,immediately flow through the cathode filaments 22 and 26 to heat them.The contacts 33 and 39, together, form a switch which is normallyclosed, but magnetically operated into open the transformer through thepower lines L L but no current will flow through the tubes I0 and Hbecause the gases in those tubes are not ionized. However, the currentinduced in the secondary winding I5 will flow through the special orbranch circuit formed of wire l9, conductor 40, spring 38 of thestarting tube, conand.

aoi' 1,969

t'acts 36 and'33, stem 34 and conductor is, wire 28, choke coil 29 andwire 39 back to the other side of the secondary winding 15. A closedcircuit now exists between the secondary winding l and choke coil 29.

There may be some .slight lag in the building up of the current' throughthe choke .coil ,29,

owing to the impedance thereof, and during this slight lag the filament'cathodes 22 and 26 will be heated somewhat by the current flowingtherethrou'gh. The magnetic field set up by the current in the chokecoil will'attract the armature orplate 31 and open the special or-branchclrcuit through the envelope 32 and .the choke'coil 29. At this openingof the special circuit, the choke coil will discharge its stored-upenergy,

and this discharge cannot occur through the tube or envelope 32 becauseof the open condition of the switch in that tube, and, therefore, therewill be a momentary discharge of the stored energy of the choke coilthrough the tubes l0 through the tubes l0 and II is sufllcient to ionizethe gas therein and strike an arc in each tube, and immediatelythereupon the illuminating cur-- rent'induced in the secondary windingsl4 and IE will flow through the tubes l0 and II and through the chokecoil 29.

Since the flow of current through the tubes l9 rent is supplied to thetransformer from the line wires L L ,.but if the currentis cut oiffrmthe primary winding 13, the=choke coil 29 will be deenergized and thecontact 36 will be urged into closed position by the spring 38, therebyplacing the apparatus automatically in a position to start a newoperation of the system whenever current is reapplied to the primarywinding l3.

While the gases contained in the tubes l9 and H to give colo'r to thelight emitted by the tubes may be varied as desired, I have found thatit is easier and preferable to rectify the current in the tube whichemits the blue light because it usually requires a higher voltage tooperate, on alternating current, a tube containing a gas that emits ared light than one that emits a blue light. Since a higher voltage wouldbe required when a. red light emitting tube is' usedas the rectifyingtube in the A. C. circuit, it leaves less available voltage'for theother tube which operates on .the rectified or D. C. For

' this reason I have found that greater efllciency is'obtained when'theA. C. tube l9 is the one which emits the blue'light, and the tube II isthen the tube which emits the red light. The colors of the. lightrayswhich are emitted by the tubes Ill and should be complementary,

so that when mixedirnmediately upon leaving the tubes, there is producedan approximately white light. r

It has long been the desire of engineers to obtain a white light closelyresembling daylight, and I have discovered that this can'be done whenthe two tubes are operated concurrently while in' close proximity to oneanother, by obtaining the proper ratio between the current densitiesThis momentary discharge of energy to that tube.

or power time two tubes. In the case of current densitieajlhave-discovered-that the current density per vsquare centimeter of crosssectional areain the blue tube should be atleast three [times that ofthe red tube and not more than six times that of the red tube, andpreferably ,the currentdensity in theblue tube should be approximately4.4 times as great as that of the red tube. when the current density inthe blue tube is 4.4 times as great as that in the red tube, and withthe tubes arranged in close relation to one another, the transmittedmixture of light from'they tubesis a white light that very closelyresembles daylight in its characteristics. In the computation is notbased upon current densities, thepower passing through the tube emittingblue light should be from one to three times that passing through thetube which emits red light. Preferably the power passing through theblue light emitting tube should be substantially twice that passingthrough the red light emitting tube, because I have found that by thisratio a white light may be obtained which has characteristics veryclosely approaching daylight. I prefer to use this ratio of currentdensities and power in the system herein disclosed and claimed.

- It will be notedthat the breaking of the special circuit through thechokecoil ionizes the gas in both tubes l0 and l l and starts the flowof illuminating current therethrough although one tube is being operatedby direct current and the other by alternating current. Hence the gas ineach tube is ionized in the same manner, regardless of the character ofthe illuminating current applied If any gaseous illuminating tube is tobe lighted or started by direct current, I

series in the special circuit, such as in series in the wire 35, so thatthe direct current passing through the special circuit, and which mustbe broken by the contacts 33 and 35, will not be too great to handle.The resistance of the choke coil 29 is not great, although that coil hassufllcient reactance when used in an A. C. circuit with a leakage typetransformer to prevent passage of heavy currents therethrough in thespecial circuit. When the choke coil is used with direct current in thespecial starting circuit, the resistance 4| should be included in seriesin the special circuit to prevent substantial short circuits that mustbe broken by separation of the contacts 33 and 3G.

{I'he gaseous I illuminating tube emitting red light will operate toproduce more light per watt of power whenoperating on direct currentthan when operating onalternating current, and since the red lightemitting tube is more ineflicient than the blue light emitting tube forlight production, it is feasible and desirable to use it in theilluminating circuit as the direct current tube. a

It will be understood that various changes in Y the details, which havebeen herein described and illustrated in order to explain the natureof'the invention, may be made by those skilled in the art within theprinciple and scope of the invention. as

expressed in the appended claims. a

I claim as my invention: i

1. In a lighting system for gaseous illuminatin tubes, a double anodelowvoltage gaseous illumi nating tube, a single anode low voltagegaseous illuminating tube, a source of alternating current, a lightingcircuit for said double anode tube inffind it advantageous to provide aresistance 4| in v eluding said double anode tube and said. source, 3

whereby current from said source will pass through said double anodetube and be rectified thereby, said single anode tube being included inseries in said lighting circuit at the cathode'side of said double anodetube, and with the anode of said single anode tube connected to thecathode of the double anode tube, whereby said single anode tube will beoperated by the rectified current from said double anode tube, and achoke coil in series with said single anode tube at a point between saidsource and said cathode of said dou- 'ble anode tube.

2. In a lighting system for gaseous illuminating tub-es, a doubleanode-low voltage gaseous illuminating tube, a single anode low voltagegaseous illuminating tube, a source of alternating current, a lightingcircuit for said double anode tube ineluding said double anode tube andsaid source, whereby current from said source will pass through saiddouble anode tube and be rectified thereby, said single anode tube beingincluded in series in said lighting circuit at the cathode side of saiddouble anode tube, and with the anode of said single anode tubeconnected to the cathode of the double anode tube, whereby said singleanode tube will be operated by the rectified current from said doubleanode tube, a choke coil, a branch circuit including said source andchoke coil, a switch device disposed within the magnetic.

field of said choke coil, included in series in said branch circuit,urged yieldingly into closed position and operable into open position bymagnetism in said choke coil when said choke coil is energized, wherebythe energy stored in said choke coil by closing of said branch circutand released by the opening of said branch circuit will produce acurrent surge through both of said gaseous illuminating tubes, causingionization of the gas therein, and through such ionization starting theflow of lighting current through said tubes.

3. In a lighting system, a double anode low voltage gaseous illuminatingtube, a single anode low voltage gaseous illuminating tube, atransformer secondary connected at its ends to the anodes of the doubleanode tube, means connecting the cathode of the double anode tube to theanode of the single anode tube, means connecting the cathode of thesingle anode tube to an intermediate point in said secondary, and achoke coil connected in series with said single anode tube, whereby thealternating current applied to said double anode tube will be rectifiedthereby and will flow through said single anode tube to cause anillumination of both tubes by the same current, said tubes containinggas which causes them to emit colored light when illuminated, the colorsemitted by said tubes being different and complementary, and said tubesbeing arranged in proximity to one another, whereby the mixing of thelight emitted by both tubes will produce an approximately white light.

4. In a lighting system, a double anode low voltage gaseous illuminatingtube, a single anode low voltage gaseous illuminating tube, atransformer secondary connected at its ends to the anodes of said doubleanode tube, a wire connecting the cathode of the double anode tube tothe anode of the single anode tube, a wire connecting the cathode ofsaid single anode tube to an intermediate point in said transformersecondary,,whereby alternating current will pass through said doubleanode tube and be rectified thereby, and the rectified current will passthrough said single anode tube, one of said tubescontaining a gas whichcauses it to emit a blue light when illuminated, and theother of saidtubes containing a gas which, when the tube is illuminated, causes it toemit a red light, the current density per square centimeter in crosssectional area of the blue tube being not less than three times as greatas that of the red tube, and not greater than six times as great as thatof the red tube, and said tubes being arranged in proximity to oneanother to cause the mixing of the light emitted from both tubes,whereby the mixed light from said tubes will closely resemble day light.

5. In a lighting system, a double anode low -voltage gaseousilluminating tube, a single anode low voltage gaseous illuminating tube,a transformer secondary connected at its ends to the anodes of saiddouble anode tube, a wire connecting the cathode of the double anodetube to the anode of the single anode tube, a wire connecting thecathode of said single anode tube to an intermediate point in saidtransformer secondary, whereby alternating current will pass throughsaid double anode tube and be rectified thereby, and the rectifiedcurrent will pass through said single anode tube, one of said tubescontaining a gas which causes it to emit a blue light when illuminated,and the other of said tubes containing a gas which, when the tube isilluminated, causes it to emit a red light, said tubes being soarrangedwith respect to one another that the light frcm said tubes willmix immediately upon leaving the tubes, and the current density persquare centimeter in cross sectional area in the blue tube beingapproximately 4.4 times as great as that in said red tube, whereby themixed light from said tubes will closely resemble day light.

6. In a lighting system, a double anode, low voltage gaseousilluminating tube, a low voltage,

single anode gaseous illuminating tube, a source of alternating currentand connections from said source to said tubes for passing alternatingcurrent through said double anode tube to be rectified thereby and forpassing the rectified current therefrom through said single anode tube,said double anode tube containing a gas causing it to emit a blue lightwhen illuminated and said single anode tube containing a gas whichcauses the tube to emit a red light when illuminated, said tubes beingarranged to cause an immediate mixing of the light emitted by saidtubes, whereby an approximately white light will be produced by themixing of.the light from both of said tubes,

the current densities per cross sectional areas of said tubes having aratio of approximately 4 to 1 in said blue and red tubes respectively,whereby the mixed light from said tubes will closely resemble day light.

'7. Ina lighting system, a double anode low voltage gaseous illuminatingtube, a single anode low voltage gaseous illuminating tube, a trans--former secondary connected at its ends to the anodes of the double anodetube, means connecting the cathode of the double anode tube to the anodeof the single anode tube, and means connecting the cathode of the singleanode tube to an intermediate point in said secondary, whereby thealternating current applied to said double anode tube will be rectifiedthereby and will flow through said single anode tube to cause anillumination of bothtubes by the same current.

HOWARD M. CAVANAUGH.

